Patent GB-588185-A (GB)
Title: Improvements in high frequency electrical oscillators
IPC: H03B9/10
Filed: 1940-08-22
Abstract: 588,185. Magnetrons. RANDALL. J. T., BOOT, H. A. H., and WRIGHT. C. S. Aug. 22, 1940, No. 1331.6. 39 (i)] In a magnetron for the generation of continuous wave or interrupted wave oscillations. a number of resonant chambers 4, Figs. 1 and 2, are formed in a block 1 of tellurium copper alloy ; the resonators 4 are connected by narrow passages 5 to a central chamber 2 in which is mounted a cathode 3, the resonators and chamber 2 communicating with side chambers 6 formed by copper discs 7 which close the sides of the block 1. Copper tubes 8 are soldered with silver solder to the block, the cathode leads 10 passing therethrough ; the cathode is carried on nickel pieces 16 which can be bent to adjust the position of the cathode, shields 17 at cathode potential preventing side movement of electrons also being mounted on the leads 10. These pass through "Pyrex" (R.T.M.) tubes 9 sealed to the tubes 8. A similar construction of copper tube 23 and " Pyrex " extension 24 are provided for the power lead 22 which is connected to a loop 19 within a resonator and connected to the block 1. Polepieces 25 of an electromagnet are placed near the side discs 7 ; cooling ribs 1<1> are formed on the block about the resonator chambers. Formulµ are given for designing oscillators of this construction. The resonators and cathode chambers may be made by drilling a block of tellurium copper alloy and the finished blook'is cleaned by a 5 per cent solution of H2SO4 and strong chromic acid, The discs 7 are sealed by gold- or silver-tinned washers or sweated in position after tinning. The Cathode, may be in the form of a disc 3, Fig. 5, arranged at the side of the resonator chambers 4, a focusing cylinder 3<1> surrounding the cathode ; a cathode may be in each end chamber 6 and the leads therefrom brought out radially as shown in Figs. 1 and 2. The resonator chambers may be in the form of long slots 4, Fig. 9, which with the cathode chamber may be formed in a block 4<1> separate from the outer closing ring 30, or bars forming the chambers may be soldered on to the ring 30. The chambers may be rectangular in crosssection. The resonators may be made to resonate at harmonics of the fundamental mode by dividing up the wall of the chamber or by differences in spacing the resonator chambers around the cathode space. A modulating or keying grid 36, Fig. 15, may be used ; a " squirrel cage " grid 37 may focus the electrons. A further grid 40 maintained at positive potential tends to make the electrons take a long path before striking the inner wall of the cathode chamber, thereby improving the efficiency. An additional space charge grid may be used. The inner wall of the block 1 may have transverse slots giving some electrons a longer path. The heater wire 12, Fig. 3, for the cathode is insulated or made of a helix of small diameter so as not to touch the cathode body 11. In large-size cathodes, the heater wires pass through nickel plugs forced into the steatite insulators 13, the cathode being supported by means of these plugs. The emitting surface on the cathode may be in the form of strips or a directly heated cathode may be used. The assembly of cathode, connections and shields may be mounted on a block and inserted as a whole into the block 1. The coupling loop 19 may have a number of turns and it may be placed in one of the end chambers 6 ; a direct connection to one of the resonators may be used instead of the loop. Water cooling may be used and tuning effected by movable plates in the spaces 6. The device may work as a detector.